The present invention relates to optical surveying and aiming. It particularly relates to apparatus of the type comprising at least: a first channel having a display unit provided with deviation measurement means; a second channel having a sighting unit and light deviating means for angularly deviating the optical axis of the sighting unit with respect to a reference direction harmonized with the center of the vision field of the display unit; and an aiming mirror inserted in a path common to the two channels (and possibly to other further channels) for modifying the orientation of these channels with respect to a scene observed. It also relates to aiming methods using apparatus of this type. The display unit is often a camera working in the visible range, an infrared camera or a telescope.